In short, the global warming deniers are as wrong as the smoke-blowers who said in the 1960s that a pack a day was fine. No one seriously argues today that tobacco isn't bad for you — and if they did, no one would listen. But the Marlboro Men of global warming still draw attention as they deny the consensus conclusion that burning fossil fuels in power plants, cars and factories is trapping heat in the atmosphere. They deny that this will raise sea levels, bring more violent storms, and worsen droughts and heat waves. What are they smoking?

Do we have a dog in this fight? Absolutely. We just think the debate should be about fact, not fiction. We are not trying to muzzle those who disagree with us. There will be plenty to disagree about in deciding what actions to take. But it is time to ignore false and misleading statements that mask the source's bias and scam the public.

With the new attention that the I.P.C.C. report brings to the science of global warming, in coming weeks more than a few serious news reporters may be tempted in the name of "balance" to quote the deniers, who have presented increasingly discredited messages: Global warming is not happening. Or if it is, it is not caused by carbon dioxide emissions or other human activity. Or, well, it won't have an impact — we'll be fine.

Fred Singer, Science and Environmental Policy Project: "Carbon dioxide is not a pollutant." Nope. Acting under U.S. Supreme Court direction, the U.S. Environmental Protection Agency found that CO2 is a pollutant because of the harm it causes.

For those who write about global warming, spreading the pronouncements of fringe "skeptics" doesn't show balance. For those who read about global warming, it equates serious climate science and evaluation of peer-reviewed reports with the declarations of individuals, most lacking academic degrees in climate research, who are often funded by those standing to profit if the United States fails to curb carbon dioxide emissions.

The attention paid to the deniers has real consequences.

For one, it puts pressure on the I.P.C.C. to censor its conclusions.

Climate "skeptics" have vilified the U.N. panel, made up of several hundred of the world's leading climate scientists, subjecting them to "abusive language on blogs, comparisons to the Unabomber, e-mail hacking, and even occasional death threats," Justin Gillis wrote in The New York Times.

"Who could blame the panel if it wound up erring on the side of scientific conservatism," he wrote shortly before the experts issued their report. The clear implication: The criticism could lead the panel to pull its punches when, he wrote, most would want "an unvarnished analysis" of global warming's risks.

More broadly, relying on the deniers to provide "balance" also helps create political pressure that makes it all the more difficult to act against global warming.

It fuels efforts in the House of Representatives to thwart sensible measures to fight climate change. A solid majority of House Republicans denies that global warming is even occurring, pointing to the alleged disagreements among scientists to justify siding with the fossil-fuel industry.

At a minimum, good journalism -- and the readers' right to be fully informed -- requires identifying a source's stake. Is the source an environmentalist or coal or oil spokesperson? Their interests are clear.

But what about those claiming expertise or academic credentials in climate science who are supported by think tanks and front groups funded by oil, coal and others with a financial stake in the debate? The reader deserves to know their potential for bias. Better yet, it's time to toss the denial machine into the bin of discredited ideas. It can keep Joe Camel company.

Dan Becker directed Sierra Club's Global Warming and Energy Program for 18 years before founding the Safe Climate Campaign. James Gerstenzang, who covered the environment for the Los Angeles Times is the campaign's editorial director.